I recently finished an animation for a drilling company. I used some free models: cars, tram, church and two other buildings. The machine itself was modelled in Inventor by company's designer. I also imported svg traffic signs from Wikipedia.
The rest was made in Blender. I used adaptive subdivision and denoising. Materials are procedural.

One section is about 160 000 tris at a base level of detail. So the whole radiator is about 1300 000 tris. That's before subdivision however. I have 2 levels of subdivision, which means 16 time increase, so about 21 000 000 tris. Plus hair strands, so you can double that.